1. Field of the Invention
The present invention relates to a method for increasing viability of animal cells in culture under hypoxia condition, more specifically, to a method for increasing survival rate of cells in animal culture under hypoxia condition by adding antibiotics to the culture medium.
2. Description of the Prior Art
Most of animal cells require oxygen as a substrate in addition to nutrients for living. Thus, insufficient supply of oxygen to cells may cause various problems in medicine and industry. For example, in developing artificial organs including artificial liver, if the supply of nutrients and oxygen is hampered by limitation of mass transfer into the cells, the cells become died, especially, in case of using encapsulated cells, oxygen transfer is a more serious problem (see: Catapano et al., Int. J. Artif. Organs, 19(1):61-71, 1996).
In case of myocardial infarction and cerebral infarction, the blockage of blood vessels by which oxygen is supplied to tissues may hinder blood flow, resulting in necrosis of the tissues (see: Selwyn et al., Ischemic heart disease, 1077-1085, In: Isselbacher et al. (eds.), Harrison""s Principles of Internal Medicine, 13th ed., McGraw-Hill, Inc., New York). In this case, an inadequate supply of glucose which is used as an energy source by cells as well as an inadequate supply of oxygen make the situation more serious.
Recently, high-density animal cell culture is one of the popular techniques used for production of recombinant proteins or for production of cultured cells. As animal cells do not have cell walls differently from microorganisms, animal cell membranes may be easily destroyed by mechanical agitation or a contact with air, which makes it very difficult to supply oxygen into culture medium by agitation, resulting in reduction of final concentration of the cells.
In order to solve the oxygen transfer problem, attempted are a method for increasing dissolved oxygen concentration by adding purified hemoglobin which can bind to perfluorohydrocarbon or oxygen; a method for increasing yield of energy production using electron acceptors such as is fumaric acid other than oxygen; and, a method for increasing available oxygen inside the cells by expressing genetically manipulated hemoglobin in the cells. Also, recently attempted is a method for increasing resistance of cardiac cells to hypoxic condition by affecting energy metabolism pathway using trimetazidine. The said methods, however, have revealed disadvantages as followings: first, there is a limitation in improving the efficacy by adding perfluorohydrocarbon or hemoglobin to a culture medium since it does not change intrinsic property of cells but simply increases concentration of dissolved oxygen or promotes oxygen transfer; secondly, there is a limitation in an effective concentration range of electron acceptors like fumaric acid since the electron acceptors become reduced; thirdly, the method for increasing oxygen transfer by expressing recombinant genes in the cells requires complicated process and is very costly.
Under the circumstances, there are strong reasons for exploring and developing an alternative method for increasing viability of animal cells in culture under a low oxygen condition.
The present inventors have made an effort to develop a method for increasing the viability of animal cells in culture under hypoxia condition, and found that the survival rate of animal cells in culture under a low oxygen condition can be dramatically increased by growing cells in a medium containing antibiotics of quinolones, quinones, aminoglycosides or chloramohenicol in a concentration range of 0.1-1000 xcexcg/ml.
The primary object of the present invention is, therefore, to provide a method for increasing survival rate of cells in animal cell culture under hypoxia condition.